Firefighters and rural residents have been on edge about wildfires all year, after the Camp Fire obliterated the town of Paradise in Butte County last November, killing 86 people — the deadliest wildfire anywhere in the United States in 100 years — and the Wine Country fires the year before destroyed more than 6,000 homes in a similar trail of death and destruction across Napa, Sonoma and Lake counties.

Yet in a run of much-needed good fortune, so far California has been spared this year.

There are still at least two months left in fire season, and hot weather is forecast over the next two weeks, so things could change. But as of this week, fewer acres have burned in California this year than in any year since 1998, according to an analysis of 25 years of federal and state fire records by this news organization.

“It’s been great. We don’t want to see fire. We don’t want to see anybody hurt,” said Scott McLean, deputy chief of Cal Fire, the state’s primary firefighting agency. “Our troops need the break. They need the rest.”

From Jan. 1 through Aug. 21, a total of 65,360 acres burned statewide on all types of land, including private property, national forests, national parks and other lands. That’s a staggering 94 percent less than what had burned last year over the same period in California: 1,096,033 acres, an area more than three times the size of Los Angeles.

More noteworthy: This year’s total is 83 percent lower than the previous 10-year average through Aug. 21, which is 387,295 acres.

On Friday, no major fires were burning anywhere in California. In fact, the U.S. Forest Service has rated most of the state as at “moderate” risk for wildfires this week, issuing a map largely colored green while major parts of Nevada, Utah and Arizona were orange and red.

There are two main reasons for the lack of catastrophic fires this year, experts say.

First, this past winter was very wet across the state. Fed by soaking atmospheric river storms that barreled in off the Pacific Ocean, the Sierra Nevada snow pack grew to 161 percent of its historical average by April 1. Lake Tahoe filled to the top and ski resorts stayed open until July.

Fires don’t burn in snow. And at lower elevations, umbrellas were out a lot, too.

Rains filled reservoirs and replenished rivers and groundwater basins that were still suffering from the state’s five-year drought, which ended in 2017. That drenched millions of acres, reducing fire risk.

Add to that, temperatures across much of California have been slightly cooler than normal so far this summer, even though other parts of the world have received record heat waves as the climate continues to warm. Record wildfires are raging in Alaska, Siberia and the Amazon rainforest, for example, and last week federal scientists reported that July was the hottest month globally ever recorded back to 1880 when modern temperature records began

“We have epic fires elsewhere,” said Craig Clements, professor of meteorology at San Jose State University and director of the school’s fire lab. “But because our weather locally was cooler and wetter, our fire danger was lower. But in the long term, the trends are showing we are going to have more drought and warmer temperatures. That’s going to affect wildfire.”

A key factor in wildfire risk in California is the moisture content of plants. Basically how much water they have soaked up. The more water they have, the more difficult it is for them to burn.

The moisture content of manzanita and chemise, two plants scientists regularly measure to gauge fire risk across California, is about 20 percent higher now in the Bay Area than average, Clements said.

So even though wet winters cause more grass to grow, he said, when larger vegetation like shrubs and trees soak up more moisture in during wet winter and spring conditions, fires that start in the grasses don’t spread as rapidly to shrubs and trees as they do during dry years. That allows fire crews to make progress before the flames explode out of control and burn hundreds of homes.

“There have been a lot of ignitions but the fires are being put out,” Clements said. “They aren’t spreading as fast this year.”

That’s what happened Friday when an ominous fire began 15 miles north of Redding, near Shasta Lake. That blaze, called the Mountain Fire, immediately re-kindled memories of the Carr Fire last August, which started when a flat tire on a vehicle caused its metal rim to spark against the road. That fire burned for a month, charring 229,000 acres around Redding, killing three firefighters and five residents, destroying 1,600 buildings and causing $1.6 billion in damage.

As soon as the Mountain Fire started Thursday, Cal Fire, the Forest Service and local fire agencies leaped into action, sending more than 500 firefighters to the blaze in meadows, rural subdivisions and oak woodlands.

Smoke rises from the Mountain Fire near Redding on Thursday. (Photo: Cal Fire)

Roughly 4,000 residents in the area near Shasta Lake were evacuated. But by Friday morning, the fire’s progress had halted at 600 acres and crews said they expected it to be out by late Saturday. Nobody died and three homes burned.

“The concern was that we are looking at triple-digit heat with winds forecast for this week coming up,” said McLean. “We wanted to get ahead of the game. There are no flames there no, just a few hot spots.”

An analysis by this news organization of fire and weather records over the past 25 years shows that four of the five worst fire years back to 1994 all occurred after drier-than-normal winters and and similarly, four of the five mildest fire years, including this year, all occurred after wetter-than-normal winters.

There are exceptions. In late 2016 and early 2017 there was a very wet winter. But dry conditions followed in October and by November, heavy winds knocked down power lines across the state, sparking fires across Napa, Sonoma and Lake counties.

With forecasters calling for hot weather over the next two weeks, fire crews are on alert, McLean said, adding that he hopes for rain in October to dramatically cut fire danger.

“We can’t be complacent,” he said. “We still have a long way to go. September and October are historically our worst months for fires. It only takes one spark.”

Paul Rogers has covered a wide range of issues for The Mercury News since 1989, including water, oceans, energy, logging, parks, endangered species, toxics and climate change. He also works as managing editor of the Science team at KQED, the PBS and NPR station in San Francisco, and has taught science writing at UC Berkeley and UC Santa Cruz.